New lower unit question

cptvic · Posted: Mon Jul 30, 2018 8:18 am Post subject: New lower unit question

We replaced our lower unit on our 2006 honda 90. Mechanic told us to change gear oil in about 20 hrs. Said thats tecommended.we change our oils at season end about 100hrs.
We were wondering if it would hurt to wait or should pull out and change it i think we are already over 30 hrs on new unit.
Any thoughts and why.

srbaum · Posted: Mon Jul 30, 2018 8:46 am Post subject:

It is a very good recommendation to change oil of any piece of new machinery, after it has run for a few hours. Even though we all hope that no debris or machine filings are inside of the geracase or crankcase, the reality is that even the best and most accurate machine work can still leave small particulate of machined items in the oil (usually in suspension while the machinery is operating).
Not changing the oil puts you at risk of those small particles causing damage to the bearings, shaft or gears.
I overhaul outboards often and have seen premature damage (in many engines and gearcases), caused by not following oil change recommendations.

srbaum · Posted: Mon Jul 30, 2018 9:38 am Post subject:

One other addition to my note made on this post...
New seals are not immune from being defective, or improperly installed, so that is another very good reason to change and inspect the old oil. If a seal has a minor leak and water contaminates the oil, the sooner it is caught, the less likely that long term damage will occur.
I recently purchased an engine to go through and sell... The owner said that the engine leaked crankcase oil, dripping out the bottom of the engine over time. Upon disassembly, I found that the factory forgot to install one of the lower seals in the 3 year old engine...

ssobol · Posted: Mon Jul 30, 2018 10:58 am Post subject:

BrentB · Posted: Mon Jul 30, 2018 12:03 pm Post subject:

There is 10 - 20 hours break in procedure on new LU and need to change its oil and washers, and inspect oil metal pieces and water.

BrentB · Posted: Mon Jul 30, 2018 2:02 pm Post subject:

Fill unit with manufacturer's required gear oil to recommended level.
Adjust RPM at idle to manufacturer's specifications.
Proper shift adjustment is essential.
Jumping out of gear: If the unit will not stay in gear, the clutch dog has probably been rounded off. Rounded clutch dogs are caused by, but not limited to, improper shift cable adjustment, inadequate shift travel, idle RPM too high, and/or shifting too slow. Rounded clutch dogs are not covered by warranty.
Avoid full throttle starts.
Do not operate at constant speed for extended periods.
Shift into forward gear a minimum of 10 times during break-in, with moderate engine speed after each shift.
Do not exceed 75% of full throttle during the first 5 hours of operation.
During the next 5 hours, full throttle should not be maintained for long periods.

cmetzenberg · Posted: Mon Jul 30, 2018 3:11 pm Post subject:

srbaum · Posted: Mon Jul 30, 2018 4:58 pm Post subject:

Conrad's comment answers to Ssobol, as to why the oil is changes and inspected early on. Usually no problems are found...